Method of polishing hollow stem valves



April 10, 1945. v A. T. CQLWIELL 2373,4591

METHOD OF POLISHING HOLLOW STEM VALVES Filed Dec. 20, 1941 out with extreme m m, macs Apmicafiam December 20;. mm swam 1m 42mm 4 Elaiims;

neIates: m the: m: the: intenfcns f mucw as hollow puppet valves.

Mare specificzmy the invention. nemfies tn the Eliminaticm cf mimics; 01" cmcks in the interim surfaces c-fi sad poppet as as the the pmductim cf manna: valves; of superior resulting in. for we wives.

The interior surface 01: a homm' puppet; vama fihe interim smgface cf tha stem: cf such a valve, must; be as ccmfiimmu's. as pcssfbfe tore;- the cf elaborate polishing: cnemticns are used in remcve teal marks or scratches by reaming tools 01" in the waive cavities. Such tau]; marks or scratches are very dangerous they fbrm fatigue Foci during: use of the warm zesulfiing, in same mstances, in w complizte failure of valva, ince the walve'sfiem, in. operatfcn, is subfected to drcumfirenfiah Scratches m the stem BEBE: ous. Such cirmnmferenfifal swatches readily form the loci for cmcksv in the valve stem because the stem is subjected to axial streses shacks as the valve 0 and closes in an engme. The repeated pounding at tremendcus 'speeds; which the valve stem must; undergo; in high speed, cempressiom engines; suchv as aircraft engines. has greatly increased the Potential dangers 01: such scratches.

f; is cflsimble t0 make file hell-w valve and cient as leao as $0 wstraimtawhichitissnbjm- Since the valve stem is subs! in very little forcesortendingtoexpandthe same, it follows that the stem resist the tension stresses. it will not fail use of any mdial stresses.

In accordance with, this mventim the Exterior wallotahnllowvalvesfiemissubjectedtcms Polishing treatments tor'remuvmg as many tool marks and scratchs as possible. The rotary polishing operation, how'evez, even when carried care, will leave at least a few These scratches may even but nevertheless loci.

In accnrdance with this invention the m w Polishing oneratmn is renewed up with g Iona-4 or swabbm pc afiicm. swahbfng nemnvea; scratches amthcugiaz it may mm mmtmdmali m the However, we lbugfiu'dfimli am no? dimemus since as explained abme, fihe valve stem is mm: to) hikh afinasem while; the Icngi may me as loci far nadimli cracks; they dB um: farm. such: fer cmcka fcmefi flue Eu =i and their presence i nui'kas a, result of the flhezcime; the: damthicker stem.

with thin walk; which.

- in lcngitudmal cross section mm the interim of the valve stem and a sfimnger stem results requiring weight cf the valve.

Ifi. them am obfect: of this imwenficm m pmwide hmfl'ow stemmed pcpnet valves which are free fmm. interfcrscmfichas which same as fa;- tigue fact for cracks: develuneri as a; of loading 01 fihe mm A fitmther object of the is m cbli'terafie circumierenfiial l scratches in film Interim" e of a hollow valve stem and thereby pmdimce: astronger valvei A fimtherobifecfz o1 invention is #0 pmwide a methedi of pcfishingr the film-mm ct hallcw valves: which results in the pr of stronger valves;

A. still further object of fihig invention isto pmvide a. method 01' poifsmnm cs hollcw valves including mtary i 1 axfali swabbing operations.

A further cbfect of the invention. is to prmiuce a hullcw stemmw, poppet valve which wrath has longiwdinafly a 2;. matches in its Interior surface.

Other further object; of the: invention beapnarenttathusemthemtrmthe t'oIIcwing detailed deacrflpflcn cf the aanexcd'e sheet oi drawings 1 w by at w example, mustratea an embodiment of the 0n the diawiug:

igure 1 is a broken mmmm clam 2mm view of a,- mtary polishing {at the interior of a hclloiu Puppet valve which is shown igure 2 is a broken tary elevation view of a. reciprocating or swahbfnx Wm polishing machine t0 obliterate the circumferential scratches remaining In the valve shmm in longitudinal cross-section: 1

figure 3 is an. enlarged Ionaihldinn cross-sec:-

scratches 2| remaining therein.

tional view of a poppet valve body after the rotary polishing operation;

Figure 4 is a view similar to Figure 3 illustrating the valve body after the longitudinal or swabbing type polishing operation;

end of the stem. The stem has a cylindrical bore I i, extending inwardly from the nubbin end thereof and merging into a tapered or conical bore H which extends to the head cavity l3 of the hollow head Illa. The tapered bore l2 provides a thickened throat portion Illd for the blank.

Theblank ill can b prepared by forging, for example, as described in the McBride et al. Patent 1,984,751, o by any other suitable process.

In acc :dance with this invention, the cylindrical bore H and tapered bo're I! of the stem Nib are reamed to size with a reaming tool. The reaming tool may leave circumferential or hellcally extending marks ll in the interior wall of the stem, which must be removed. For this purpose the valve blank III is slipped over a rotating polishing tool l5 sized tosnugiy engage the walls of the bores I l and II. For this purpose the tool I! has a tapered leading end lid to engage the wall of the tapered bore l2 and a trailing cylindrical end l5b to engage the wall of the bore H. The tool i5 is mounted on a horizontal shaft I which can'be rotatably mounted in a support ll and driven through a pulley l8 by a driven belt I9.

As shown in Figure 5, the tool i5 is covered with a helically vwound strip of abrasive paper or cloth such as emery cloth.

For the first polishing operation a No. 80 eme y cloth is used. Such a cloth has abrasive particles sized to pass a screen having eighty openings per linear inch.

The interior of the stem lilb is thus polished in a circumferential direction by the abrasive cloth and, since the tool it rotates circumferential scratches will remain in the walls of the bores H and l2.

After the interior walls of the stem are polished to remove scratches capable of being removed by a No; 80 abrasive clbth, the tool II, or another.

tool, is provided witha finer abrasive cloth, usually having abrasive particles of about No. 120

size. The rotary polishing operation is continued as illustrated in Figure 3, the walls of the bores II and i2 still have circumferentially extending These scratches may be of microscopic size, but are still highly detrimental-since they can form fatigue loci for cracks when the valve is axially loaded as in operation. i

It is, thus, highly desirable to remove the circumferentially extending scratches 2|.- In accordance with this invention these scratches are "removed by a reciprocal or swabbing tim polishasvaese ing operation. The rotary polished blank it can be mounted in a polishing machine 22 as shown in Flgm'e 2 and the tool I! can be driven by a reciprocating shaft 23. The shaft 23 can have a cross head 2! thereon driven by a pin 25 from a driven disk or pulley it. The pulley 26 is adaptedtobedrivenbyabeltfl. Thetool iilwill not rotate in the machine 20 but will reciprocate into the bores II and I! of the valve stem llb. The tool I! used for the swabbing type polishing treatment can have an abrasive covering thereon at least as fine or finer than the abrasive used for the last rotary polishing operation.

The reciprocating polishing treatment is continued until all of the circumferentially extending scratches 2i are removed. A valve stem interior as shown in Figure 4 then results. As therein shown the bores H and i2 have the walls thereof free from circumferential scratches but containing a plurality of longitudinal or axialscratches 28. These axial scratches will not form loci for cracks developed because of axial tension load on the valve stem. Since the radial load on the valve stemis relatively negligible the iongitudinal scratches 28 are immaterial and do not in any way weaken the valve. I

In this method of polishing, therefore, the valve stem interior is subjected to successive rotary polishing treatments withabrasive material of progressively increasing fineness. After the last rotary polishing treatment with'very fine abrasive material the valve stem interior is further polished in a longitudinal direction with an abrasive at least as fine as the one used in the last rotary polishing step. The longitudinal polishing is continued until all circumferentially extending scratches are removed from the interior wall of the stem.

According to a modified process of this invention the longitudinal polishing operation may alternate with the rotary polishing treatment as long as the last polishing treatment is in a longitudinal direction. For example, the tool marks produced by the reaming or drilling toolsin the valve stem can first be treated with a rotating polishing tool carrying abrasive material up to a No. size. This rotary polishing treatment or treatments is then followed by a longitudinal swabbing polishing treatment with a No. abrasive. The longitudinal treatment is then next followed with a rotary treatment with a No. abrasive, and the final treatment can be in a longitudinal direction with a No. 180 abrasive. or even as fine as a No. 320. Instead of using abrasive cloth on either or both the rotating or reciprocating tools l5, polishing stones carrying abrading particles of the proper size can be used. For example, the tool II, as shown in Figures 6 and '3', can carry a'pair of hollow polishing stones it shaped to fit around the end of the tool. These stones 30 are urged outwardly by means of a spring 3i which can extend through a transverse bore 32 inthe tool.

Studs 33 can extend throughthe stones 30 and be threaded into the tool I. The stones 30 can slide over the studs.

'In this spring-urged stone type of polishin tool the stones are resiliently urged apart so that they will snugly engage the walls of the bores II and ii to polish these walls. The stones can be made with abrasive particles of the same fineness described above in connection with the polishiugcloth 2|.

Fromthe'above descriptions it will be understood that this invention now provides stronger hollow stemmed pop t valves by obliterating all circumferentially extending scratches in the inner wall of the valve stem.

It will, of course, be understood that various details of the process may be varied through a wide range without departing from the principles of this invention and it is. therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims. r Iclaim as my invention: v

1. The process of polishing the stem interior of a hollow stemmed poppet valve to increase the fatigue resistance thereof which comprisessuccessively subjecting the valve stem interior" wall to the action of abrasive material of progressively increasing fineness. applying the abrasive material to the stem interior wall in a series of the interior of the stem in a rotary direction,

repeating the rotary polishing treatment with abrasive material of progressively increasing fineness, and finally swabbing the rotary polished Ill valve stem and abrasive material which isat least as fine as the material used in the last rotary polishing step, such non-rotative longitudinal movement being continued throughout the entire final step. and being efi'ective to re-' move circumferentially extending scratches from the interior surface of the stems.

3. The method of increasing the fatigue resistance of thin-walled hollow stemmed metal poppet valves by removal of metal from the valves which comprises inserting an abrasive material carrying tool in the valve stem, effecting relative rotation between the valve stem and tool to polish the interior of the stem in a rotary direc-- tion, repeating the rotary polishing treatment with abrasive material of progressively increasing fineness, and thereafter swabbing the rotary polished valve stem interior in a longitudinal direction only with abrasive material which is at least as fine as the material used in the last rotary polishing treatment for removing circumferentially extending scratches from the interior of the stem.

valve stem interior by a non-rotative longitudinal reciprocatory relative movement between the 4. The method of polishing the stem interior of a hollow poppet valve and increasing the fatigue 

